The study conducted over a period of 12 years revealed that use of statins at any time had no effect on Alzheimer's disease or strokes.

Researchers studied 929 Catholic clergy members with an average of 75 years old, free of dementia at the beginning of the study and enrolled in the Religious Orders Study, an ongoing study of aging and Alzheimer's disease.

In the beginning 119 people were taking statins and during the 12-year follow-up, 191 people developed Alzheimer's disease, of whom 16 were using statins at the start of the study.

Dr Zoe Arvanitakis, study author and Associate Professor of the Department of Neurological Sciences at Rush University Medical Center in Chicago and member of the American Academy of Neurology said that contrary to previous reports statins offers no protection against Alzheimer's disease.

"Some studies have suggested people taking cholesterol-lowering drugs are less likely to have Alzheimer's disease, but our longitudinal findings found no relation between statin use and Alzheimer's," said Arvanitakis.

"The study also found no association between taking statins and a slower cognitive decline among older people," she added.

In addition, brain autopsies of more than 250 people who died during the study also revealed that statin use at any time during the course of the study had no effect on pathology of Alzheimer's disease or strokes.

However, Arvanitakis said that the study was limited as there were relatively few statin users among those who died but future studies will look at the possibility of associations of statins with other pathologic changes of Alzheimer's disease.